On youtube there are very nice examples of 3D reconstruction with 2D drawings or photos as for example this one:

How can this type of illusion be recreated?

We will create the following illusion:

This gives the following picture:

To achieve this we start by taking a picture in the final decor with a clear indication of the perspective, if possible an A4 sheet which will facilitate the reproduction. Here we have put a sheet on top of the Thymio II robot. One has to be careful to be able to put the camera back in the same position for the final photo.

Then we add an item that is wanted in 3D. Alternatively, one can take a picture with an existing object, as is probably the case in the example film at the start of the page. The important thing is to overlay the 3D object with an indication of the perspective.

Then one "resets the page" so as to distort the image. The aim is to find the A4 sheet in its original size. This type of operation can be done with software such as Photoshop, for example. Software like camscanner also perform this type of operation.

This page can then be printed and used in the scene which has been prepared. In our case the squirrel has been cut out and the shadows have been re-drawn by hand. If one takes a photo of a 3D object, the shadows will be included in the photo. If one adds a 3D object with image editing software, shadows will need to be added. Be careful that the shadows correspond to the shadows of the rest of the image.